The present invention relates to a material for medical use and a process for preparing the same, and more specifically a material for medical use which is applicable to an artificial organ and an artificial viscus, furthermore, which is applicable as a wound covering material, a wound prosthetic material, a wound curing material, a postoperative adhesion-preventing material and the like, and a process for preparing the same.
It has long been known that, when a living tissue has some disorders, is damaged, or has dysfunction, an artificial material is used for replacement, prosthesis, or prevention of adhesion of damaged parts, and it has been conventionally investigated to use a synthetic high molecular material or a material originating from a living body for vessels, air tubes, esophagi, valves, various viscera, and wounds. Such a material is required to satisfy various requirements such as, having an affinity for a living body; having a compatibility with body fluids such as blood, or tissues; having neither toxicity nor antigenicity; and having a mechanical strength as predetermined depending on the implant site.
Generally, a material originating from a living body may possibly cause disorders associated with implantation or immunological responses. However, a collagen, a material originating from a living body, has excellent affinity for a living body and tissue-compatibility, possesses low antigenicity. Collagen also facilitates activity on elongation and proliferation of host cells, as utilized as a medium for cell culture, and has styptic activity. It also has excellent properties as a material for medical use since it is completely absorbed in a living body. However, when only the collagen only is used, it is difficult to form therefrom a material which has a high invading ability into cells and a high proliferating ability for host cells, and also has a considerable mechanical strength. Therefore, collagen has been conventionally used as a composite material with a synthetic high molecular material.
Such a composite material for medical use is produced by forming a covering layer of collagen comprising an alkaline-solubilized collagen or an enzyme-solubilized collagen, having reduced antigenicity, on a surface of the synthetic high molecular material. The synthetic high molecular material may comprise a silicone, a polytetrafluoroethylene, a polyethylene, a polypropylene, a polyethylene terephthalate, a polyurethane, a polyvinyl alcohol and a nylon in the form of film, sheet, woven fabric, non-woven fabric, tube, sponge and the like. The composite may be formed by a coating or a flowing method, and by solidifying the covering layer of collagen by a freeze-drying method and the like. The surface of the synthetic high molecular material is subjected to a hydrophilization treatment by plasma irradiation and the like, so as to improve the affinity for living tissue or the covering layer of collagen.
Another material for medical use has been proposed wherein a material degradable in a living body, having a considerable mechanical strength, which is hydrolyzed or enzymatically decomposed and absorbed in a living body, is combined with collagen.
The material for medical use is produced by solidifying a covering layer comprising an alkaline-solubilized collagen or an enzyme-solubilized collagen, by the above method, on a surface of a material degradable in a living body in the form of film, sheet, woven fabric, or non-woven fabric, comprising a polyglycolic acid, a copolymer of glycolic acid and lactic acid, or a mixture of a polyglycolic acid and a polylactic acid. When the material is implanted in a living body, not only collagen but also the degradable material is hydrolyzed or enzymatically decomposed, and absorbed in the living body, so that it is not necessary to remove the material by conducting another operation again or an endoscopy. The material degradable in a living body is also subjected to a hydrophilization treatment with plasma irradiation as well as the synthetic high molecular material.
However, such a material has a disadvantage in the transfixing property that, when an intermediary material comprising a material degradable in a living body in the form of woven fabric or non-woven fabric, equipped with a covering layer of collagen, is sutured with an organ or a wound, a surgical needle cannot easily pass through a hole in the material. Even if the needle can pass through the hole, force added to the covering layer of collagen may destroy the covering layer of collagen having a small mechanical strength. This material has another disadvantage in that although the affinity for a collagen solution is improved by plasma irradiation on the surface of the intermediary material, the covering layer of collagen may peel from the intermediary material after implantation because of insufficient adhesion between the intermediary material and the covering layer of collagen. In such a case, it is required to conduct another operation to implant the material.